Oligocene Sediments Research Articles

A new species of Chaneya from the Oligocene Ningming Formation, Guangxi, South China

Chaneya ningmingensis sp. nov. is described from the Oligocene Ningming Formation in Guangxi Zhuang Autonomous Region, South China. Fruits of the new species are characterized by bearing five persistent, free, large petals, each containing five craspedodromous, longitudinally subparallel primary veins, and their thickened central disk bearing one whorl of five free, orbicular ovaries. The discovery of C. ningmingensis provides the evidence of the occurrence of Chaneya Wang et Manchester in Oligocene sediments of South China. This is the first Oligocene record of Chaneya from East Asia. Considering the continuous occurrence of Chaneya in the Cenozoic deposits from the early Eocene to the Miocene, East Asia may be a center of diversification and differentiation for the genus Chaneya.

The Paleogene vegetation and petroleum system in the tropics: A biomarker approach

The present study investigates the biomarker signatures of sediments and crude oils to infer the paleovegetation from the two petroleum systems of Assam Basin, eastern India. They are classified as the Paleocene-middle Eocene and the middle Eocene-Oligocene petroleum systems. The sediments are oil and gas prone with an early catagenetic stage of thermal evolution. Here we report tricyclic diterpanes such as rimuane, pimarane, rosane and isopimarane along with tetracyclic diterpanes: ent-beyerane, phyllocladane, kaurane from Paleocene-Eocene coal-bearing sediments and crude oils. These diterpane biomarkers attest dominant contribution from conifers, possibly from Podocarpaceae and Araucariaceae. However, diterpanes are not detected in Oligocene sediments and oils. Crude oils from both Paleocene-Eocene and Oligocene reservoirs and organic rich sediments contain angiosperm biomarkers such oleanane and related triterpanes along with bicadinane, a biomarker specific for the Dipterocarpaceae family of angiosperms. The equatorial position of India during early Paleogene along with the presence of angiosperm signatures including Dipterocarpaceae and gymnosperms reflect the emergence of tropical rainforest elements in eastern India. Absence of diterpenoids in Oligocene samples and difference in angiosperm parameters from Paleocene-Eocene samples suggests a change in source vegetation and organofacies.

A new quantitative approach to identify reworking in Eocene to Miocene pollen records from offshore Antarctica using red fluorescence and digital imaging

Abstract. Antarctic palaeoclimate evolution and vegetation history after the formation of a continent-scale cryosphere at the Eocene–Oligocene boundary, 33.9 million years ago, has remained a matter of controversy. In particular, the reconstruction of terrestrial climate and vegetation has been strongly hampered by uncertainties in unambiguously identifying non-reworked as opposed to reworked sporomorphs that have been transported into Antarctic marine sedimentary records by waxing and waning ice sheets. Whereas reworked sporomorph grains over longer non-successive geological timescales are easily identifiable within younger sporomorph assemblages (e.g. Permian sporomorphs in Pliocene sediments), distinguishing non-reworked from reworked material in palynological assemblages over successive geological time periods (e.g. Eocene sporomorphs in Oligocene sediments) has remained problematic. This study presents a new quantitative approach to identifying non-reworked pollen assemblages in marine sediment cores from circum-Antarctic waters. We measured the fluorescence colour signature, including red, green, and blue fluorescence; brightness; intensity; and saturation values of selected pollen and spore taxa from Eocene, Oligocene, and Miocene sediments from the Wilkes Land margin Site U1356 (East Antarctica) recovered during Integrated Ocean Drilling Program (IODP) Expedition 318. Our study identified statistically significant differences in red-fluorescence values of non-reworked sporomorph taxa against age. We conclude that red fluorescence is a reliable parameter for identifying the presence of non-reworked pollen and spores in Antarctic marine sediment records from the circum-Antarctic realm that are influenced by glaciation and extensive reworking. Our study provides a new tool to accurately reconstruct Cenozoic terrestrial climate change on Antarctica using fossil pollen and spores.

Mid-Cenozoic ostracod biostratigraphic range extensions and taxonomic notes on selected species from a new Oligocene (Duntroonian–Waitakian) fauna from southern New Zealand

AYRESS, M., ROBINSON, J.H. & LEE, D.E., March 2017. Mid-Cenozoic ostracod biostratigraphic range extensions and taxonomic notes on selected species from a new Oligocene (Duntroonian–Waitakian) fauna from southern New Zealand. Alcheringa 41, 487–498.This paper discusses a highly diverse assemblage of Ostracoda, particularly biostratigraphically useful species, from a richly fossiliferous shallow-marine deposit of late Oligocene age on Cosy Dell farm, near Waimumu, Southland, New Zealand. The ostracod fauna, consisting of 126 species, is yet to be fully analysed, although it is clear that this new window into the nearshore fauna of the mid-Cenozoic provides the earliest records of many characteristic extant New Zealand genera and species, including several species hitherto only known as far back as the early Miocene (Otaian–Altonian New Zealand local Stages). Finding these younger species in an Oligocene deposit was unexpected and indicates that our current knowledge of mid-Cenozoic ostracod age ranges, particularly for nearshore species, is incomplete. Using nannofossils and molluscs, the Cosy Dell deposit is dated as late Oligocene (Duntroonian or lower Waitakian local Stages) in age; therefore, the new ostracod species occurrences described here are considered valid range extensions. Although the biostratigraphic application of the benthonic ostracod species discussed is limited owing to the effects of sedimentary facies and other palaeoenvironmental factors, the ostracod fossil record does include significant extinction and inception events that offer correlative potential for mid-Cenozoic stratigraphical studies. This study identified a need for modern illustration of many species, and we provide scanning electron microscope illustrations of those Cosy Dell taxa previously considered biostratigraphically useful, as support for species identification and associated biostratigraphic conclusions.Michael Ayress [mike.ayress@rpsgroup.com], RPS ichron Group, Gadbrook Business Centre, Northwich CW9 7TN, UK; Jeffrey Robinson [jeffreyhrobinson@yahoo.co.nz] and Daphne Lee [daphne.lee@otago.ac.nz], Geology Department, University of Otago, Dunedin, New Zealand

New clues on anuran evolution: the oldest record of an extant hyloid clade in the Oligocene of Patagonia

Despite the enormous diversity of the extant South American batrachofauna, its fossil record is sparse. Few pre-Neogene anuran remains have been attributed to extant taxa and, although some have been considered neobatrachians their relationships with extant groups are still mostly uncertain. In this context, a series of fossils recently collected in Oligocene sediments of central Patagonia are assigned to Odontophrynidae. This assignation is supported by an exclusive combination of characters, including extensive frontoparietals, in medial contact and deflecting posteriorly, with crescent-shaped posterolateral projections; robust pterygoid anterior ramus, reaching the planum antorbitale, projecting dorsally; notched premaxillary pars palatine; dentate vomers, narrowly separated medially; robust neopalatines, narrowly separated medially, bearing a conspicuous ridge, and with expanded lateral edges. The well-preserved fossil specimens were considered representative of a new genus and species, Chachaiphrynus lynchi. The presence of an Oligocene Odontophrynidae in central Patagonia, about 500 km south from the southern-most extant distribution of the group, would be associated with the more benign climate inferred in this region during the Paleogene. At the same time, this record represents the single pre-Neogene certain record of an extant clade deeply nested in Hyloidea, providing an exceptional high-quality calibration point to temporally frame the anuran phylogeny.http://www.zoobank.org/urn:lsid:zoobank.org:act:AA043DC2-BCA5-4301-8FB0-FEB56B0F4404

Facies analysis and biostratigraphy of the Miocene sequence, Cairo-Suez District, Egypt

Miocene siliciclastic-carbonate deposits are widely exposed in Cairo-Suez District, Egypt. These deposits are underlain and overlain by continental sediments of Oligocene and post Miocene, respectively. Three stratigraphic sections were investigated at Gabals Geneife, Homeira and Gharra. Lithostrtigraphically, the Miocene sequence could be differentiated into two main rock units representing shallow deposits with relatively intermittent deep marine incursions. These are from base to top, Gharra Formation and Genefe Formation. Detailed macrofossils investigations led to the recognition of four macrofossil zones, namely Alectryonella plicatula-Crassostrea frondosa Range Zone, Echinolampas amplus-Scutella ammonis Range Zone, Chlamys (Macrochlamys) sardoa-Chlamys (Argopecten) submalvinae Range Zone, and Chlamys gentoni-Pecten (Oppenheimopecten) benedictus-Pecten (P.) ziziniae Assemblage Zone. Microfacies analysis and identified taxa indicated that the Miocene sequence was deposited in transgressive-regressive cycles ranged from near shore, warm shallow inner to middle shelf marine environments with storm influence during the accumulation of the oyster banks.

Tectonic and climatic signals in the Oligocene sediments of the Southern North-Sea Basin

Tectonic and climatic signals in the Oligocene sediments of the Southern North-Sea Basin

Foliage accumulations of Osmunda lignitum (osmundaceae) in the Oligocene of northern Italy and western Germany

Accumulations of Osmunda (Plenasium) lignitum (Giebel) Stur fern foliage have been recently recovered in the Oligocene deposits of northern Italy at Cassinelle and western Germany at Niederpleis-1 (Sankt Augustin; Winterscheid 2006). They morphologically match other European records distributed from the Eocene to the Oligocene (– early Miocene). Material from both sites represents sterile pinnae compressions with preserved leaf anatomy. The data obtained on leaf cuticles correspond to most of the previous findings from Germany (Geiseltal, Seifhennersdorf, Haselbach) but cast doubts on some others based on dispersed cuticles (e.g. Zülpich). Comparison with living species of Osmunda (Plenasium) from east and south-east Asia revealed only minor differences in the epidermal structure and stress the close relationship with Osmunda banksiifolia (C. Presl) Kuhn distributed along valley streams from China, Japan to Indonesia, New Guinea and Philippines.

Enamel microstructure defines a major Paleogene hippopotamoid clade: the Merycopotamini (Cetartiodactyla, Hippopotamoidea)

We present new material of the selenodont anthracothere Hemimeryx blanfordi from the Oligocene deposits of the Bugti Hills (Balochistan, Pakistan), collected between 1999 and 2002. This is the first undisputed Oligocene occurrence of the species, previously known from the early Miocene of Pakistan. Investigation of the molar enamel microstructure reveals a surprising mono-zonal Schmelzmuster, already detected in some middle to Late miocene selenedont anthracotheres. We include this observation combined with a morphological revision of H. blanfordi and a cladistic assessment of the dental evidence, to propose a new phylogenetic hypothesis regarding Hemimeryx and its close relatives. We confirm the clade including advanced bothriodontines, which we erect to a tribe rank and name Merycopotamini. The South Asian origin of Merycopotamini is consistent with hypothesized subsequent dispersal events of Merycopotamini from Asia to Africa.

Revision der Flora aus den oberoligozänen Seeablagerungen der Grube „Stößchen“ bei Linz am Rhein (Rheinland-Pfalz, Deutschland)

Revision der Flora aus den oberoligozänen Seeablagerungen der Grube „Stößchen“ bei Linz am Rhein (Rheinland-Pfalz, Deutschland)

Gas accumulations in Oligocene–Miocene reservoirs in the Alpine Foreland Basin (Austria): evidence for gas mixing and gas degradation

Two petroleum systems are present in the eastern (Austrian) sector of the Alpine Foreland Basin. Whereas oil and thermogenic gas in Mesozoic and Eocene reservoir rocks have been generated beneath the Alps in Lower Oligocene source rocks, relative dry gas in Oligocene–Miocene clastic rocks deposited in the deep marine basin-axial channel system (Puchkirchen Channel) is interpreted as microbial in origin. Detailed investigations of the molecular and isotope composition of 87 gas samples from 86 wells, representing all producing fields with Oligocene and Miocene reservoir rocks, suggest that the presence of pure microbial gas is rare and limited mainly to the northern basin flank (e.g., KK field). All other fields contain varying amounts of thermogenic gas, which has been generated from a source rock with oil-window maturity. A relation with the underlying thermogenic petroleum system is obvious. Upward migration occurred along discrete fault zones (e.g., H field) or through low-permeability caprocks. Local erosion of Lower Oligocene sediments, the principal seal for the thermogenic petroleum system, as well as a high percentage of permeable rocks within the Puchkirchen Channel favored upward migration and mixing of thermogenic and microbial gas. All gas samples in Oligocene–Miocene reservoirs are biodegraded. Biodegradation and the formation of secondary microbial gas resulted in gas drying. Therefore, the gas samples analyzed in this study are relative dry, despite significant contributions of thermogenic hydrocarbons. Biodegradation probably continues at present time. The degree of biodegradation, however, decreases with depth.

Humulago, a Replacement Name for Fossil Humularia Dorofeev (Cannabaceae) non Extant Humularia Duvigneaud (Fabaceae)

Humulago Doweld nom. nov. (Cannabaceae) replaces the fossil Humularia Dorofeev 1982, non extant Humularia Duvigneaud 1954 (Fabaceae). Two fossil species, based on fruits from the Oligocene sediments of Western Siberia (Russian Federation) are recognized as Humulago tymensis (Dorofeev) Doweld comb. nova and Humulago reticulata (Dorofeev) Doweld comb. nova.

Reconstruction of atmospheric CO2 during the Oligocene based on leaf fossils from the Ningming Formation in Guangxi, China

Recently, several leaf fossils with good cuticles were discovered from the Oligocene deposits in Guangxi, China. The high fossilization potential of these leaves and easily identifiable stomata and epidermal cells make them an excellent source for CO2 reconstruction. In this study, atmospheric CO2 of the Oligocene is reconstructed using the mechanistic-theoretical model based on stomatal data, photosynthesis and gas exchange control and using an alternative method based only on stomatal ratio. Fossil leaves of Buxus ningmingensis, Chuniophoenix slenderifolius and Cephalotaxus ningmingensis, two angiosperms and one gymnosperm, were considered. It was found that some differences were present between the results obtained by the two methods. The SR-based method yields a somewhat narrower CO2 range (from 355 to 578ppmv) than the model approach (from 255 to 972ppmv) which encloses the former range. The CO2 results derived from the three species using the two approaches are overlapped to a high degree with CO2 data from other terrestrial plants and phytoplankton material. More data provided by different proxies are desirable to unravel the interactions between atmospheric CO2 and climate change for the Oligocene.

A new assemblage of stem pecoran ruminants from the Oligocene Chitarwata Formation, Bugti Hills, Baluchistan, Pakistan: Paleoenvironmental and paleobiogeographic implications

A new assemblage of stem pecoran ruminants from the Oligocene Chitarwata Formation (lower Bugti Member), Bugti Hills (Pakistan), consists of three identified genera and another indeterminate ruminant. Although limited, the dental and postcranial material is sufficient to identify the genera Amphitragulus and Mosaicomeryx, two common forms known from middle to late Oligocene deposits of Europe, thus reinforcing the ‘middle’ Oligocene age of the lowermost Chitarwata Formation. Mosaicomeryx is reported for the first time from the Indian Subcontinent and this occurrence considerably expands its geographical distribution. A new genus and species, Paalitherium gurki, is erected on the basis of an unusual and unique association of characters on its lower molars. The unclear definition and occurrences of? Gelocus gajensis Pilgrim, 1912 are re-examined in the light of new data from the Bugti and Zinda Pir areas (Pakistan). The new ruminant fauna from Paali is clearly distinctive from the early Miocene assemblage known from Bugti. In accordance with other fossil evidence, the ruminant fauna described here suggests the existence of a tropical forested environment under monsoonal regime with soft food supplies during the time of deposition of the lowermost Chitarwata Formation.

Oldest meiolaniid turtle remains from Australia: evidence from the Eocene Kerosene Creek Member of the Rundle Formation, Queensland

Poropat, S.F., Kool, L., Vickers-Rich, P. & Rich, T.H., September 2016. Oldest meiolaniid turtle remains from Australia: evidence from the Eocene Kerosene Creek Member of the Rundle Formation, Queensland. Alcheringa 41, XX–XX. ISSN 0311-5518.Fossil meiolaniid turtles are known only from South America and Australasia. The South American record is restricted to the Eocene, and comprises two genera: Niolamia and Gaffneylania. The Australasian meiolaniid record is more diverse, with three genera known (Ninjemys, Warkalania and Meiolania); however, the oldest known specimens from this continent are significantly younger than those from South America, deriving from upper Oligocene sediments in South Australia and Queensland. Herein, we describe the oldest meiolaniid remains found in Australasia to date. The specimens comprise a posterior peripheral, a caudal ring, and an osteoderm, all of which derive from the middle–upper Eocene Rundle Formation of The Narrows Graben, Gladstone, eastern Queensland. Despite their fragmentary nature, each of these specimens can be assigned to Meiolaniidae with a high level of confidence. This is particularly true of the partial caudal ring, which is strongly similar to those of Niolamia, Ninjemys and Meiolania. The extension of the Australasian meiolaniid record to the Eocene lends strong support to the hypothesis that these turtles arose before South America and Australia detached from Antarctica, and that they were consequently able to spread across all three continents.Stephen F. Poropat*† [stephenfporopat@gmail.com], Australian Age of Dinosaurs Natural History Museum, The Jump-Up, Winton, Queensland 4735, Australia; Lesley Kool*† [koollesley@gmail.com] and Thomas H. Rich [trich@museum.vic.gov.au], Melbourne Museum, 11 Nicholson St, Carlton, Victoria 3053, Australia; Patricia Vickers-Rich [pat.rich@monash.edu], Monash University, Wellington Rd, Clayton, Victoria 3800, Australia. *These authors contributed equally to this work. †Also affiliated with Monash University, Wellington Rd, Clayton, Victoria 3800, Australia.

Sedimentological architecture, shelf-edge trajectories and evolution of an Oligocene reservoir, East Nile Delta

Abstract3D seismic data and wireline logs from 17 wells in the onshore East Nile Delta were utilized to study the stratigraphic architecture and evolution of Oligocene deposits. The Oligocene is readily recognized on seismic cross-sections by a series of northward prograding clinoforms. The Oligocene sequences show lateral facies changes from fluvial to deepwater via a shelf-edge delta. Such deltaic features include distributary channels, interdistributary bay fill, and a delta plain and front, gradually changing downslope into prodelta and slope deposits. The slope deposits include three main depositional elements: a deeply incised channel, a complex of laterally switched leveed channels and lobes, and crevasses and frontal splays. These depositional elements are formed in the main western slope basin and local eastern intraslope ponded sub-basin. The reactivated E–W- and NW-trending faults as well as NE–SW inverted structures are the main controls on slope physiography that formed the main corridors for Oligocene sediment distribution. Two main globally correlated Oligocene sequences are encountered being separated by the major drop in global eustatic sea level at 28.1Ma. The lower Oligocene sequence has two main stages: (1) the formation and filling of a basal canyon; and (2) the formation and progradation of shelf deltas to form shelf-edge deltas, and then progradation with an ascending shelf-edge trajectory (clinoforms 1). The upper Oligocene sequence is characterized by accretionary shelf-edge deltas with descending and then flat trajectories (clinoforms 2–4). The frontal splay and lobe complex exhibits potentially favourable reservoir continuity and areal coverage followed by the slope channels.

Seismic Interpretation of the Nam Con Son Basin and its Implication for the Tectonic Evolution

DOI:10.17014/ijog.3.2.127-137The Nam Con Son Basin covering an area of circa 110,000 km2 is characterized by complex tectonic settings of the basin which has not fully been understood. Multiple faults allowed favourable migration passageways for hydrocarbons to go in and out of traps. Despite a large amount of newly acquired seismic and well data there is no significant update on the tectonic evolution and history of the basin development. In this study, the vast amount of seismic and well data were integrated and reinterpreted to define the key structural events in the Nam Con Son Basin. The results show that the basin has undergone two extentional phases. The first N - S extensional phase terminated at around 30 M.a. forming E - W trending grabens which are complicated by multiple half grabens filled by Lower Oligocene sediments. These grabens were reactivated during the second NW - SE extension (Middle Miocene), that resulted from the progressive propagation of NE-SW listric fault from the middle part of the grabens to the margins, and the large scale building up of roll-over structure. Further to the SW, the faults of the second extentional phase turn to NNE-SSW and ultimately N - S in the SW edge of the basin. Most of the fault systems were inactive by Upper Miocene except for the N - S fault system which is still active until recent time.

New Cenozoic dragonflies from the Most Basin and Středohoří Complex volcanic area (Czech Republic, Germany)

ABSTRACTDiscovery of new dragonflies from Oligocene and Miocene deposits of the Most Basin and České Středohoří Complex volcanic area in northern Bohemia and Saxony (Germany) is reported. Aeshna zlatkokvaceki sp. nov. is the first described dragonfly from early Miocene salmon-pink baked clays of Želénky near Duchcov. Its fore wing venation pattern seems to be closely related to that of Aeshna turoliana Riou and Nel, 1995, known from late Miocene of La Montagne d’Andance in Ardèche, France, and Aeshna solida Scudder, 1890, known from late Eocene of Florissant in Colorado, USA. A new occurrence of a libellulid dragonfly ?Onychothemis rihai in the Libkovice Member of Most Basin confirms the links to the Cypris Formation in Sokolov and Cheb basins reflecting similar habitats as was already shown on the basis of reconstructed palaeovegetation and shared thermophilous and accessory floristic elements. Other fragmentary fossil material from different localities are discussed.http://zoobank.org/urn:lsid:zoobank.org:pub:7A3BB1C3-5A70-4058-86A5-731B58C0ADC3

First record of Cricetops rodent in the Oligocene of southwestern China

The muroid Cricetops Matthew and Granger, 1923 commonly occurred in the Oligocene terrestrial deposits in central and northern Asia. Here we report the first record of Cricetops in the southern part of Asia. Isolated rodent molars named as a new species, Cricetops auster sp. nov., were discovered from the early Oligocene sediments at the Lijiawa locality in Yunnan Province in southwestern China. Compared to previously known Cricetops, C. auster is smaller than Cricetops dormitor Matthew and Granger, 1923 and Cricetops aeneus Shevyreva, 1965, but larger than Cricetops minor Wang, 1987. The cusps of C. auster are less conical. The ridges and crests are longer, higher and thicker. Relatively long and high crests, ridges and arms extending from the main cusps in the new species make those cusps more crescent in appearance than in C. dormitor, C. aeneus and C. minor. C. auster is a rare species in the Lijiawa mammalian fauna. Well-developed shearing tooth crests and ridges of C. auster probably suggest a different diet from the Cricetops from the northern part of Asia.

DIRECTIONS ACTUALIZATIONS OF STRATIGRAPHIC SCHEME OF OLIGOCENE DEPOSITS OF THE NORTHERN BLACK SEA REGION AND ADJACENT PART OF THE UKRAINIAN SHIELD

The article provides a description of local stratigraphic units of the Stratigraphic Scheme of the Oligocene deposits of the Northern Black Sea region and adjacent part of the Ukrainian Shield based on critical revision of lithology and paleontology data, of using biostratigraphic developments of different micro and macro fossils. Research has been carried out within requirements of Stratigraphic Code of Ukraine (2012). Modern International Stratigraphic Chart (2012-2015) and modernized Regional Stratigraphic Scale of Paleogene of Ukraine (2013) were accepted in the proposed scheme. History of selection the Borisfen Formation of Planorbellian regional stage, the Molochna Formation of Molochnaian regional stage, the Serogozy, Askaniia and Gornostaivka Formations of Kerleutian regional stage are given. Detailed litological-paleontological characteristics of these formations and information about their stratotypes are presented. These units have been correlated with the Oligocene stages of International Stratigraphic Chart. The Borisfen and Molochna Formations correspond to Rupelian stage. The Serogozy Formation is correlated with Upper Rupelian – Lower Chattian. The Askaniia and Gornostaivka Formations correspond to Chattian stage. Synonyms and gomonyms of local stratigraphic units varying in ranks of Oligocene of the Northern Black Sea region and adjacent part of the Ukrainian Shield are described.